Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/36—Polyalkenyalcohols; Polyalkenylethers; Polyalkenylesters
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
  • G03C1/775—Photosensitive materials characterised by the base or auxiliary layers the base being of paper
  • G03C1/79—Macromolecular coatings or impregnations therefor, e.g. varnishes

Definitions

• This invention relates to forming a photographic paper having low oxygen permeability and photographic elements formed utilizing this paper.
• U.S. Pat. No. 4,283,496--Aono et al discloses the formation of a photographic layer having a single layer of polyvinyl alcohol polymer or other polymer that lowers oxygen transmission through said paper.
• U.S. Pat. No. 2,358,056--Clark discloses a photographic paper having a layer of barium sulfate dispersed in polyvinyl alcohol between the photographic emulsion and the paper.
• U.S. Pat. No. 3,277,041--Sieg et al discloses the use of a cross-linked polyvinyl alcohol polymer to increase the water resistance of a photographic paper.
• WO 93/04399--Lacz et al discloses a system to prevent oxygen permeation of color photographic papers by impregnation of the surface of the paper with polyvinyl alcohol. While the Lacz system is successful in producing a paper having low oxygen leak rate, the process for manufacturing is somewhat slow in that two applications of polyvinyl alcohol with a drying step in between are required.
• U.S. Pat. No. 5,185,230--Bagchi et al discloses applying an oxygen barrier material around individual coupler or other photographically active particles.
• a method of forming a photographic paper comprising applying to a base paper a polyvinyl alcohol of low molecular weight in a water solution that contains greater than 15 percent by weight of said polyvinyl alcohol.
• the invention further provides a paper comprising wood fibers and polyvinyl alcohol of molecular weight of between a number average of 2,000 and 10,000.
• the invention has numerous advantages over prior processes and products.
• the process allows the impregnation of sufficient polyvinyl alcohol polymer to reduce oxygen transmission without interfering with the coating of the normal polyethylene layer that serves as a base for the photosensitive emulsion layers on the photographic paper.
• the process of the invention allows formation of a photographic element that has improved image stability without a change in the image-forming materials.
• the photographic elements of the invention have the advantage that the photographic paper may be formed utilizing substantially the current paper formation process, with the addition of a single polyvinyl alcohol polymer solution application apparatus.
• the solution of low molecular weight polyvinyl alcohol would be applied to the paper by dipping it in a tank of the solution prior to the final drying of the paper during formation.
• the low molecular weight polyvinyl alcohol may be loaded into water solutions at high concentrations such that the pick-up of material in one pass is sufficient to provide an improvement in the oxygen barrier properties of the paper sufficient to have an improvement in the photographic affect.
• the low molecular weight polyvinyl alcohol solutions allow loading of the paper at speeds substantially the same as those operating in the normal paper-making mode without the polyvinyl alcohol added to the paper.
• Any low molecular weight polyvinyl alcohol that provides oxygen leak rate protection with rapid absorption into the paper for barrier protection may be utilized.
• Those suitable have been found to have a molecular weight in the range of between about 2,000 and about 10,000 number average molecular weight with a weight average molecular weight of between 6,000 and 30,000.
• a preferred number average molecular weight range has been found to be between about 4,000 and about 9,000
• concentrations of polyvinyl alcohol in water that produce this viscosity depend on the molecular weight of the polyvinyl alcohol, and on the degree of hydrolysis; for example, the viscosity, h, increases approximately exponentially with concentration, c:
• This invention includes the use of solutions of low molecular weight polyvinyl alcohols that result in high amounts of polyvinyl alcohol being incorporated into the paper in one application, and that these amounts produce papers with desired low porosities, oxygen leak rates, and oxygen permeabilities.
• Solution concentrations can be as high as 50 percent by weight polyvinyl alcohol, but are preferably in the range of 20 to 40 percent by weight. These solutions can also contain sodium chloride, to impart antistatic properties to the paper after drying, or sodium bicarbonate for pH control, or surfactants to reduce foaming or other needed ionic or nonionic materials.
• This invention includes polyvinyl alcohols with degrees of hydrolysis between about 70 and 100 percent, but preferably greater than about 85 percent.
• Polyvinyl alcohols with the lower degrees of hydrolysis have larger oxygen permeabilities, but said polyvinyl alcohols also produce solutions of lower viscosity.
• larger amounts of less hydrolyzed polyvinylalcohol can be imbibed, and this can compensate for the poorer barrier properties of the dried form of less hydrolyzed polyvinyl alcohol.
• the polyvinyl alcohol impregnated papers of the invention may be utilized in conventional photographic papers. The formation of such photographic papers utilizing polyvinyl alcohol impregnated paper is disclosed in U.S. Ser. No. 756,262 filed Aug. 19, 1991 and coassigned with this application. It is also disclosed in WO Pat. No. Publication 93/04399 that corresponds to United States patent application also incorporated by reference.
• the polyvinyl alcohol polymer is impregnated in any amount that provides substantial oxygen impermeability. Generally a suitable pick-up range is impregnated between about 7 and about 20 weight percent of the dry paper weight for an effective barrier to oxygen infiltration and relatively low cost. A pick up of about 10 to 15 weight percent of the dry impregnated paper weight is preferred for low cost with good oxygen permeability properties.
• the impregnation of the invention results in a paper that in the preferred embodiment does not have a polyvinyl alcohol layer above the surface but has polyvinyl alcohol impregnation concentrated near both surfaces of the paper. It has been found that the one pass of the paper in polyvinyl alcohol solution results in sufficient pick-up of polyvinyl alcohol to provide the oxygen impermeability desired.
• the range of polyvinyl alcohol in the solution is between about 20 and about 50 weight percent with a preferred amount being about 20 to about 40 weight percent for adequate impregnation of the paper.
• the PVA sizing solution also generally contains up to 1 percent sodium chloride based on the PVA solids.
• the sodium chloride provides internal conductivity to the paper such that it is not susceptible to static electricity buildup.
• a preferred solution viscosity of the polyvinyl alcohol impregnation solution is between about 200 and about 500 centipoise at 50° C.
• Impregnation of the polyvinyl alcohol into the paper is such that an oxygen impermeable (zone) is created on at least the side onto which the photographic emulsions will be placed.
• a suitable temperature for the PVA impregnation is about 50° C.
• the PVA sizing as set forth above will result in a zone of substantially complete impregnation of at least the upper 40 microns on the emulsion side of the paper.
• the emulsion side is the side of the paper that was against the wire of the paper-making machine. The side of the paper that was against the wire during paper formation is called the wire side, and the other side of the paper is called the face side.
• the amount of impregnation of polyvinyl alcohol on the back side (face side) of the paper away from the emulsions is less critical, although substantial impregnation is considered necessary to prevent curl.
• conventional weight photographic paper has an overall thickness of about 200 microns, and the sizing method of the invention will result in face side impregnation of at least about 20 microns. It is preferred that impregnation be at least 50 microns on the emulsion (wire) side of the paper in order to provide an adequate oxygen barrier.
• substantially complete impregnation is intended to indicate that substantially all voids between wood fibers have been filled by the polyvinyl alcohol polymer.
• the sizing operation also may apply fillers, pigment, brighteners, dyes, hardeners, and other addenda typically utilized in size solutions.
• Non-contact drying immediately after polyvinyl alcohol impregnation is applied to dry the surface of the paper to be non-tacky such that contact with the dryer drums does not cause adhesion of wet polymer to the dryer drums. Further, the non-contact drying serves to aid in concentration of polyvinyl alcohol nearer the surface of the paper such that oxygen impermeability results with less use of polyvinyl alcohol. The non-contact drying preferably removes at least about one-third of the water in the support.
• the paper prior to any impregnation with polyvinyl alcohol be dried to below about 10 percent moisture and preferably below about 5 percent moisture for greater polyvinyl alcohol pick-up when dipped into the polyvinyl alcohol solution. It is particularly desirable that non-contact drying be carried out, as there is a greater tendency for the polyvinyl alcohol solution at the surface to stick to the drying drums if it is tacky upon contact with them.
• the paper sheet that is impregnated with the polyvinyl alcohol may be of any desired basis weight. It is generally preferred that the paper sheet have a basis weight of between about 25 and about 50 lbs/1000 sq. ft to provide a conventional feel and handling to the impregnated paper. A heavier weight paper of up to 80 lbs/1000 sq. ft. may be preferred for display purposes.
• the polyvinyl alcohol impregnated papers can be utilized in the formation of photographic elements which, after exposing and processing, generate colored images which are surprisingly stable to light. Furthermore, the images exhibit neutral fade to light; the yellow, magenta, and cyan image dyes fade at the same rate, thus prolonging the useful lifetime of the print.
• the light stabilities of the yellow and magenta image dyes are usually inferior to the light stability of the cyan image dye leading to an objectionable non-neutral fade of the color print.
• the light stabilities of the yellow and magenta image dyes are improved substantially, while the light stability of the cyan image dye remains largely unaffected leading to greater image stability and neutral color fade.
• the yellow and magenta image dyes which benefit from the impregnated supports are formed by the reaction of oxidized color development agents with 2- and 4-equivalent image couplers such as open-chain ketomethylenes, pyrazolones, pyrazolotriazoles, and pyrazolobenzimidazoles. Typically, such image couplers are ballasted for incorporation in high boiling coupler solvents.
• Couplers which form magenta dyes upon reaction with oxidized color developing agents are described in such representative patents and publications as: U.S. Pat. Nos. 2,600,788; 2,369,489; 2,343,703; 2,311,082; 3,152,896; 3,519,429; 3,062,653; 2,908,573, and "Farbkuppler-eine Literaturubersicht,” published in Agfa Mitannonen, Band III, pp. 126-156 (1961).
• Couplers which form yellow dyes upon reaction with oxidized color developing agents are described in such representative patents and publications as: U.S. Pat. Nos. 2,875,057; 2,407,210; 3,265,506; 2,298,443; 3,048,194; 3,447,928; 5,021,333, and "Farbkuppler-eine Literaturubersicht,” published in Agfa Mitannonen, Band III, pp. 112-126.
• UVA ultraviolet light absorber
• the UVA's are substituted phenylbenzotriazoles which are described in such representative patents as U.S. Pat. Nos. 4,853,471; 4,790,959; 4,752,298; 4,973,701; 4,383,863; 4,447,511; and references listed therein.
• Specific UVA's described in this invention are shown in structures V, U, and R.
• the preferred UVA's are the liquid type to minimize crystallization and surface blooming problems observed with solid UVA's.
• Various layers to convert the paper support into a light reflecting print material such as silver halide emulsion layers, subbing layers, interlayers, and overcoat layers are provided onto the paper support of the invention.
• the paper of the invention when used in a photographic element would be coated with a layer of silver halide emulsion containing cyan forming color coupler, a layer of silver halide emulsion containing a magenta dye forming coupler, and a layer of silver halide emulsion containing a yellow dye forming coupler.
• conventional polyethylene extrusion coated layers may be provided on the paper support.
• the silver halide emulsion employed in the elements of this invention can be either negative-working or positive-working.
• the silver halide emulsions employed in the present invention preferably comprise silver chloride grains which are at least 80 mole percent silver chloride and the remainder silver bromide.
• a group of polyvinyl alcohols was evaluated for their ability to provide an improvement in oxygen leak rate after a single pass through a bath of polyvinyl alcohol during formation of the paper.
• a polyvinyl alcohol of the earlier referenced Lacz et al application was utilized as a comparison. Also for comparison, the polyvinyl alcohol was applied to a single side of the paper to determine whether single-side application would provide sufficient impregnation for oxygen barrier properties.
• the photographic paper support by the examples was produced by refining a pulp furnish of 50% bleached hardwood kraft, 25% bleached hardwood sulfite, and 25% bleached softwood sulfite through a double disk refiner, then a Jordan conical refiner to a Canadian Standard Fineness of 200 cc.
• the surface sized support was calendered to an apparent density of 1.00 gm/cc. This support was extrusion coated on the emulsion-facing side with polyethylene containing 12.5% TiO 2 , and other addenda at 5.6 lb./ksf coverage. The opposite side was coated at 6.0 lb./ksf with just polyethylene.
• Table 1 lists a group of suitable polyvinyl alcohol materials of low molecular weight indicating their properties.
• Table 2 is a listing of the results of the tests. As illustrated by Table 2, a leak rate of below about 100 is considered as a test result that is indicative of a possibly commercially suitable material. While it is noted that in the above-referenced Lacz et al application, a leak rate of below 30 mL/m 2 per day was considered as necessary for substantially improved photographic performance, it is known that materials formed by this test apparatus that have an oxygen leak rate of below about 100 are likely when formed upon a commercial machine to reach the preferred oxygen leak rate of below 25 mL/m 2 per day. Therefore, results below are considered satisfactory if the leak rate is below about 100 mL/m 2 per day, as this is equivalent to a production paper of oxygen leak rate of below 25 mL/m 2 per day.
• the oxygen leak rate was measured, using the same apparatus and test conditions as in WO93/04399 and U.S. Ser. No. 039,340 filed Apr. 16, 1993 of Lacz et al hereby incorporated by reference. Nitrogen gas was introduced as the carrier gas in both the upper and lower chambers. After a suitable amount of time (30-180 minutes), the oxygen sensor was inserted into the lower chamber exhaust stream. Once equilibrium was established, the rate of oxygen reaching the sensor was recorded as the oxygen leak rate. The oxygen leak rate thus represents the rate that oxygen is reaching the sensor from 1) outgassing of the sample, 2) leaks in the system, and 3) leaks through the edge of the paper and diffusion through the polyethylene layer.

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• Spectroscopy & Molecular Physics (AREA)
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• 1994
  • 1994-08-26 US US08/296,774 patent/US5576152A/en not_active Expired - Lifetime
• 1995
  • 1995-08-22 EP EP95202267A patent/EP0698816B1/de not_active Expired - Lifetime
  • 1995-08-22 DE DE69502896T patent/DE69502896T2/de not_active Expired - Fee Related
  • 1995-08-25 JP JP7217868A patent/JPH08106140A/ja active Pending

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